1. The problem statement, all variables and given/known data How can you use a charged rubber rod to induce a net negative charge on a metal sphere? 2. Relevant equations None. 3. The attempt at a solution OK, I understand the basics, but it seems like this question should be worded so as to inducing a net "positive" charge on the metal sphere. It seems key to me that the rubber rod would have to be negatively charged, and if we're talking about induction (the two objects not touching), it would seem intuitive that bringing the rubber rod near the sphere would cause electrons to migrate to the side of the sphere opposite the sphere. If the sphere had a ground, some electrons would completely leave the sphere and the cutting the ground would leave the sphere with a net positive charge. But how the heck can you get the sphere to have a negative charge via induction? Or is there a means by which that rubber rod can be positively charged?